The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
The power consumption and the construction size are critical and must therefore be minimized for the use of a clutch of this type in the drivetrain of a power vehicle. There are also further demands: A regulation range of the transmitted torque which is so wide that a driving off from stationary is possible without slip, on the one hand, and complete separation is possible, on the other hand, also for noise reasons; and, finally, fast response to be compatible with electronic drive regulation systems (ESB, ABS, etc.).
A clutch of this type is known from EP 940 286 A2. The magnetic field is generated by a coil fixed with respect to the housing here. The field lines are relatively long due to the manner of construction of the magnetic coil with its yoke, which reduces the size of the active part of the magnetic field, that is its part acting on the magnetorheological liquid. An air gap thereby also arises between its yoke and the rotating parts, in particular the disks, which has to have a substantial width for tolerance reasons. The magnetic field lines are thereby interrupted and the magnetic field acting on the magnetorheological liquid is further weakened.